Voice operated mechanism



A ril 15, 1941. H. w. DUDLEY ,2

' VOICE. OPERATED MECHANISM Filed March 51, 1939 15 Sheets-Sheet 1 FIG!SOUND R EC [IFIERS VO/C/NG LOCK :10. .CONSONANT LOCK AMI? ' A TTO/QNEVApril 15, 1941. -H. w. DUDLEY ,5

' -VOICE OPERATED MECHANISM Filed March 31, 1939 15 Sheets-Sheet 2 FIG.2

BARS

/Nl EN7'OR hi W. DUDLEY V ATTORNEY Y April 15,.1941- H. w. DUDLEY2,238,555

VOICE OPERATED MECHANISM- Filed March 31, 1939 15 Sheets-Sheet 3 FIG. 3

SELECTOR CONTROL APPARATUS INVE/V TOR H. W DUDL E V B) ATTORNEY A ril15, 19.41. H w, D DLEY 2,238,555

VOICE OPERATED MECHANISM Filed March 31, 1939 15 Sheets-Sheet 4 GROUNDUPPL IEO FROM INVENTOR /1! H. 0 00; E V

April 15, 1941; H. w. DUDLEY VOICE OPERATED MECHANISM Filed March 31,1939 15 Sheets-Sheet 5 INVENTOR ht n. DUDL EY a0; @05 605 805 aoz a i AT TORNEV April 15, 1941. w DUDLEY 2,238,555

V0 ICE OPERATED MECHANISM Filed March :51, 1939 15 Sheets-Sheet 6 lNl ENTOR By HWDUOLEV A TTORNEV April 15, 1941. H. w. DUDLEY VOICE OPERATEDMECHANISM l5 Sheets-Sheet 7 Filed March 31, 1939 INVENTOR HW. DUDLEYATTORNE V April 15, 1941.

H. w. DUDLEY VOICE OPERATED MECHANISM Filed March 31, 1959 15Sheets-Sheet a I/VVE/VTOR /i W DUOL E Y A T TOR/V5 V April 15, 1941. H.w. DUDLEY VOICE OPERATED MECHANISM 15 Sheets-Sheet 9 Filed March 31,1939 FIG. 17

INVENT OR H; W. .DUDLEV- A TTORNE Y April. 15, 1941.

GR/OUP GROUP GROUP H. w. DUDLEY VOICE OPERATED MECHANISM Filed March 31.1939 FIG; /8

WORD TEST BARS 15 Sheets-Sheet 10 nnnnn'n //V [/5 N TOR HWDUDLEV I ByATTORNEV Apr-i115, 1941. DUDL Y 2,238,555

VOICE OPERATED MECHANISM Filed March .31, 1939 15 Sheets-Sheet 11 I FIG./.9 FIG-.20 FIG. 2/

INVENTOR Byh. "(DUDLEY ATTORNEY April 5, 1941- 5 H. w DUDLEY 2,238,555

VOICE OPERATED MECHANISM Filed March 31,1939 15 Sheets-Shet 12 FIG 22INVENTOR By M WDUDLEY A T TORNEV April 15, 1941. H. w. DUDLEY 2,238,555

. VOICE OPERATED MECHANISM I Filed March 31, 1939 15 Sheets-Sheet 13 I IF1623 R=RING E=BE SELECTOR 33.9 CON TROL APPARA TUS I=FILL E=SELL T=TENINVENTOR h. W DUDLEY er .4 TTORNEYI April 15, 1941. H. w. DUDLEY VOICEOPERATED MECHANISM 'Filed March 51, 1939 15 Sheets-Sheet 14 FIG. 24

INVENTOR 8 MW. DUDLEY ATTORNEY April 15, 1941. w, DUDLEY I 2,238,555

VOICE OPERATED MECHANISM Filed March 31/1939 15 Sheets-Sheet 1s.

lNl/ENTOR H W DUDL E) A T TOR/VEV dependent variable has a fundamental,or not 'over lll -cycles per: second-while engaged Patented Apr. 15,1941

stares PATENT 2,238,555 VOICE orsnsrnp MECHANISM Homer W. Dudley, GardenCity, N. Y., assignor to Bell lielephone Laboratories, Incorporated, NewYork, N. Y., a corporation or New York Application March 31, 1939,Serial No. 265,269 35 Claims. (01.179-18) Thisinvention relatesto speechoperated devices particularly of the type in which a speech message isanalyzed to cause mechanical operations determined by the word contentof the message.

In a preferred embodiment the invention relates to an automatictelephone system-in which a connection to a wanted subscriber isestablished by switching devices automatically controlled byvoicetoperated equipment responsive -to an oral pronouncement of theoffice and number of the wanted subscriber. Voice operated 1 dialing ina.telephone system may be taken as typical of various applications ofthe present invention to voice operated mechanisms'whe'reeach desiredmechanical operation is effected only when a combination of sounds in acertain sequence is received by the mechanism.

In order that mechanical operations may be performed directly inresponse to spoken sounds it is necessary to analyze. thesounds andderive therefrom a set of parameters which collectively of speech.Further, the chosen parameters need not be entirely independent providedtheir 1111111- ber be increased sufliciently to make up for their lackof independence. In accordance with the 5 preferred form of thisinvention the chosen parameters maybe the amounts of power present in'selectedgsubb'ands of the speech frequency range.

For example, the speech frequency range by means of band-pass filtersmay be divided into 0 ten subbands collectively extending over thefrespeech wave is divided so that each slotted bar define each sound anddistinguish eachssound of importance in speech from all other speechsounds. In choosing the set of parameters to be employed for thispurpose use is made of the fact that one set of parameters can besubstituted for another set without any'loss of definition so long asthe number of independent parameters remains unchanged.

As pointed out in my earlier U. S; Patent No. 2,194,298 of March 19,1940, the number of movable or variable elements oi the vocal systemthat are controlled as parameters to give the desired speech productionand are movable or variable J substantially independently of one anotherby the muscles of the vocal system is small. In other v words, thenumber of variables 'or parameters that can be-controlled substantiallyindependently in speech'production is small; being of the order 61' ten.Moreover, for each of the physical elements the minimumtime it can gothrough a, complete cycle of change in position is not less than about=.1""se'cond.- Consequently each ininspeech production. 9

Therefore, the speech defining signals. into whichthe-spoken message istranslated for producing the desired mechanical ration may be is capableof assuming, any one of several positions depending upon the power levelin its assigned subband for each spoken sound. It,

r therefore, follows that the slotted. bars in response' to a spokensound will assume relativepositions individual to that sound" and meanstesting for the relativeactuated positions of the slotted bars may beutilized in producing the desired mechanical operation.

In accordance with a preferred embodiment of the voice operatedmechanism of this inven tion the speech soundsare picked up by a microphone and transmitted to an amplifier whose gain is automaticallyadjusted for a constant speech level without, however, disturbing therelative loudness of the sounds making up a given word. The relativelyconstant volume output of this amplifier is next analyzed byamultiplicity 40 of band-pass filterseach passing a different subband'of the speech frequency 'range and collectively passing theimportantfrequencyfrange of I speech sound, for example, ,from 0 to 7500 cycles.The output of each filter. then goes to arectifier to produce asyllabicchange .in current .proporfrequency" Y tional to the amount oi power inthe particular frequency band passed by its filter. This syllabicchanging power from each rectifier energizes 'an electromagnet foractuating a resonance bar which may be similar in character to the codesignals derived from the mess e, providing the -v.deriv e''d ignals=glveas many independent variable i quantities orparameters as the number ofinbars employed in teletypewriters. These resonance bars,-therefore,have deflections varying with the amount .of power inthe particularsubbands. The. resonancebars may ha es'lots .cut

4 dependent .l ariables involved 1 in the production 5.; in them in uchman ith ti th c circuits that canbe controlledthereover in actest barwill thereupon be actuatedv to operate rents for a given sound line upone set of slots in the bars so that a testing device individual to thatparticular sound can fall into the aligned slots. With the slots soaligned. a sound test bar, representing that particular sound will enterthealigned slots to permit the actuation of said sound test bar by amain hall or equivalent construction. Each subsequently spoken sound ina similar manner will cause the actuation of a sound test bar individualto that sound.

In a particular embodiment it may be desired, to close a certainelectrical contact in response .to the spoken key-word one and adifferent contact for each of the other numerals 2 to 9,

inclusive. including I, each contact being closed only when the phoneticsounds received by the 4 mechanism are received in the same sequence asthey occur-in the keyword. In suchafsicase the above-described soundtest bars, 'eachni'efining a separate phonetic sound, are adapted tocontrol a series 01 groups of movable storing bars whereby the actuationof a sound test bar. defining" the first sound of a key-word will givethe first group of storing bars relative positions defining saidfirst-sound, and the subsequent sound 01' the key-word will give thesecond group' of storing .bars relative positions defining said secondsound, and so oniuntil allthe phonetic sounds oi'the given key-word aresuccessively registered in the diil'erent groups of these storing bars.All of the storing bars for registering the successive phonetic sounds01 a key-word may be so notched 'or slotted that when the registration,therein the phonetic sounds oi a given keyproduce mechanical movementsdefining the respective phonetic sounds;

Fig. 5 is a plan viewof the resonance bars 01' Fig. 4 slotted in such amanner that their relative positions after actuation by the speechcurrents may define the individual-phonetic soundsrepresented thereby;

Figs. 6 to 11, inclusive, represent the various,- stages in theoperation or a sound test bar as controlled by the resonance bars in themechanismpf Fig. 1;

Figs. 12 --A to l2-D, inclusive, illustrate in schematic form how asound test ba defining a voiced stop sound may be prevented romoperating when the sound set up in the resonance bars is of a difierenttype;

Figs. 13'-A to 13--D, inclusive,

' barsis 'of a diilerent type;

operation of the sound test bar for the second word is completed a wordtest bar defining the said key-word will, enter the aligned slots in theactuated groups of storing bars and such a word the desired electricalcontact which is individual words can be similarly registered to operatecontacts individual to each word or group of sounds.

Thus. in a machine switching telephone system, for example, the callingdial at the telephone station'may be eliminated and the subscriberupon'initiating a call transmits-the ofiice and number of the wantedline by pronouncing the same in the telephone transmitter in the samemannerhe would ii. he were calling'from a I manual station. The registerrelays at the cen-'- tral ofilce which control the selective movement ofthe line extension switches instead 01 bein set in response to theimpulses of a dialed number are now set in response to theactuation of.the above-described contacts' which collectively and in the propersequence define all o! thespoken words making up the, desired telephonethatreachthe wanted line and the extent 01 their movement is, oicourse.determined by the combination-oi relays-so locked and the selectivecordance with well-known automatic telephone practice.

is a view perspective -o i-. pa;t of the m hs ism' oi, mv ws t n e fspok enwprd intoit'sdiscrete phonetic sounds to 75 Figs. 14A to 14-D,inclusive, schematic iorm how a sound test bar defining an unvoiced stopsound may be prevented from operating when the sound set up in theresonance bars is of a diflerent type;

Figs. 15-A to 15-1), inclusive,vill ate in schematic form how a soundtest bar defining an unvoiced non-stop sound may be prevented fromoperating when the sound set up in the resonance bars is oi a differenttype;

- of Fig. 2 on which the successivephonetic sounds of Fig. 22 asdetermined by be separately recognized by the voice operated .apparatusin performing certain operations in For the purparts of the resonancebars and are registered until the sounds 0 word have been received;

Figalfl is a pla'n view bars of Fig. 1'7;

Figs. 19, 20 and 21 are schematic views of part of the apparatus of Fig.17 showing the operation of a word test bar to'close an electricalcontact representing the key-word registered on the associated storingbars; I I

Figs. 22 and 23 when placed side by side represent schematically anotherform of this invention as applied to a dlalless automatictelephonesystem:

Fig. 24 is an enlarged view in perspectiveof sound test bars oi Fig. 22;and

' Figs. 25 to 30, inclusive, represent various stages in the operationof one of the sound test bars associated resonancebars.

Before describing in detail the appar'atusdis-, closed in the drawingsit is desirable to list the minimum number of phonetic sounds which mustresponse to the spoken message. pose-oi this specification speech soundsare divided into four groups, namely. voiced stop, sounds,

voiced non-stop sounds, unvoiced stop sounds and unvoiced non-stopsounds.

.The voice stop: sounds of the first group are three in number andcorrespond to the three sounds which in the English lan uage aredesignated by the letters 3, D and hard Giget).

The voiced non-stop sounds of the secondgroup comprise twenty-iomspunds'which may b 11-.

vided' into thirteen voweLaQre semiv'owels,'iour illustrate in schematiciorm how a sound test bar defining] illustrate in a complete keyof thegroups of storing the settings or the voicedzfricatives and twotransitionals. The thirteen vowel sounds are given below by key-wordsrather than by phonetic symbols, with the vowel sounds printed in boldface type:

be fat omit about fill chaotic tall sell rude father ask. pull fur Thefive semivowels included in the second group are the consonants of thefollowing words printed in bold face type: 1

' name lit ring The four voiced fricatives are the portions of thefollowing words printed in bold face type:

zeal azure vat then,

The two transitionals included in the second The fourth group, namely;the unvoiced nonstop sounds, comprises a total of six sounds includingtwo unvoiced tr-ansitionals, the in sound in here, and the wh sound inwhat; and four'unvoiced fricatives as indicated by the consonants in thefollowing words printed in boldface type:

seal ash fat thin This makes a minimum total of thirty-six phoneticsounds which the voice operated mecha-* judge may be registered as twoseparate sounds. the 6 sound followed by them sound in azure, and

The third groupQn'amely, the unvoiced" stop the ch sound in church maybe registered as the t sound followed by the sh sound in she. Similarly,all the vowel. diphthongs maybe registered as a combination of two vowelsounds already listed.

This soundlist is for the sole purpose of illustration. In practice moreor less sounds may be recognized as found desirable.

Referring to the form of theinvention shown in Figs. 1 to 3;, inclusive,which show in diagrammatic form so much of the apparatus of coopcratingcircuits as is necessary to understand the invention, 40 represents asubscriber's line extending to the terminals of a line finder 4|, the

brushes of which are caused to move intoposition to connect with saidline by circuits that are controlled through the contacts of the linerelay I 42 which operates at the time that the subscriber removes hisreceiver from the hook. This line finder is connected to a link circuitwhich terminates at its other end in a selective switch 43 whose brushesarecapable of movement over the terminals of a cooperating terminal bankto which compensate for variations in the volume of the received soundsso that the analyzed speech currents representing the called line willalways be the equivalent of those produced by a person talking withsubstantially the same degree of loudness and to compensate forvariations in the impedance of the calling subscriber's line the speechcurrents representing the calledtelephone num-- her are impressed uponan amplifier 46 of the type called a vogad in the communication art asshown in detail, for example, in British Patent 381,831. That is,amplifier 46 has its ain auto- .matically controlled by slow variatio aA particular circuit for such a compressor is given in Crisson Patent1,737,830 of December 3, 1929, and for the expander is given in the MathPatent 1,757,729 of May 6, 1930.

At this point in the circuit of Fig; 1 it is important to distinguishbetween currents representing voiced sounds and unvoiced sounds and,therefore, a portionof the output of vogad 6G by leads 41 is impressedupon a fundamental frequency discriminating circuit til-of such acharacter that the output current from lowepass filter 50 will besubstantially zero for all unvoiced sounds, but for voiced sounds willhave an amplitude proportional to the pitch of the fundamentalfrequency. Hence, relay 5| which by leads 52 is com nected to the outputof filter Sllwill be non-operated .for unvoiced sounds but will beoperated by all voiced sounds.

Therefore, for unvoiced sounds the output I from the additionalamplifier 5i!v because of the non-operation of relay 5! will beimpressed directly upon ten band-pass filters F1 to F10. all connectedin parallel to the output of amplifier 53. These band-pass filterscollectively. pass the frequency range of importance in speech, -sa.v

from 0 to 7500 cycles, with filter F1 passing the band from 0 to 225cycles per second; 'filter F2 passing the band from 225 to 450cycles persecond; filter F3 passing the band from 450 to 700 cycles per second:filter F4 passing the band from 700 to 1000 cycles peg second; filte F5passing the band from\1000 to 1400 cycl per second;' filters Fe passingthe band from 1400 to 2000 trunk lines extending to other selectiveswitches a such as M are connected.

switch 45, which is set in motion to select the link filters F1 toFw.inclusive, connected to switch 45 by conductors 49 for receiving thespeech currents from line 40 representing the telephone number of thecalled-party as spoken into the a transmitter at the calling station. Inorder to y cycles per second; filter F7 passin the hand from 2000 to2700 cycles per second; filter Fa. passing the band from 2700 to 3800cycles per second; filter F9 passing the band from 3800 to 5400 cyclesper second: and filter F10 passin the band from 5400 to 7500 cycles persecond; The output from each of the band-passfiltersFl to Flo isrectified by one of the rectifiers R1 to R10. and the .1 vrectifiedcurrent from eachsubband is impressed The line finder, througha suitable selection I uponone of the'electromagnets S1 tO Su) of thesolenoidal type. Therefore,.eachelectromagnet S1 to $10 attracts itsarmature'with afor'ce determined by the power level of-thatportion ofthe speech wave transmitted by its associated filter sothatelectromagnet S1 attracts its armasecond, electromagne n I with a pulldetermined by the power level in the tude with a pull determined by thepower level in the frequencywrangefroni 0 to. 225 cycles per a attractsits armature frequency range from 225 to 450 cycles per second, etc. I

The armature of each of the electromagnets S1 to S10 is suitably coupledby a multiplying lever to one of the resonance bars Ci to C10 shown moreclearly in Fig. 4. Each resonance bar-C1 to C10 is biased by means ofone of the springs 54 to a normal position whereby the left end of aslot 55 in each code bar lies against a stop v pin 56. Hence each of theresonance bars C1 to C10 by means of its associated electromagnet willbe moved from its normal position an amount controlled at each instantbythe power level in the speech frequency subband passed by the filterassociated with the corresponding electromagnet. With the reasonancebars actuated in this manner in accordance with the analyzed speech curvto an unvoiced sound. Their operation for a voiced sound is quitesimilar except that for a voiced sound, relay Ii will be operated. sothat the output of amplifier is instead of being im-- pressed directlyupon the bandvpass filters will be transmitted through an equalizernetwork. 51 and another amplifier 58 before reaching the filters.Equalizer I1 is designed to correct the natural falling oil of the upperharmonics with frequency in the case of sounds produced by the vocalcords and to make the amplitude of the fundamental and all its harmonicsmore nearly uniform as is the case with unvoiced sounds. The amount ofequalization needed can be obtained from Fig. 2 of myabove-mentioned U.8. Patent No. 2,194,298 from which it is apparent that the requiredequalization varies -from a I loss of 30 decibels at 100 cycles persecond to zero at 3000 cycles per second; and that for frequencies above3000 cycles per second a gain is needed for the equalizer instead of aloss. However, such a gain would lead to increasing the line noise byamplification, so, from 3000'cycles to the upper end of the speech bandit is more desirable to have zero loss and such a condition may beassumed for the .circuits of Fig. 1 herein. This equalization producedby network 51 makes each subband of the speech frequency range equallyuseful in determining what sound test bar representing a given phoneticsound may be operated as otherwise significant amounts of energy incertain of the upper subbands might,

'sition and cause a false operation. Equalizer I'I,

therefore, reduces the amplitude of the funda; mental and the majorharmonics to a lever more nearly equal to the higher harmonics and thenamplifier 58 is employed to raise the level of the fundamental and itsharmonics to the level desired to secure the selective operation of theresonance bars.

It may be found helpful to rt an equalizer after amplifier ll to corrector the increasing amounts of energy in the upper subbands as comparedwith the'lower subbands passed by the passed subband as one proceedsfromfilter F: to filter F10; for example, filters F1 and F: pass bands 225cycles. in. width while filter F10 passes a band 2100 cycles wide. Thiscorrection 5 produced by equalizer 60 may amount to a loss of l'decibelper channel starting with the channel containing filter F2.

As additional aids in preventing false operation, applicant in thepreferred embodiment of the invention employs a so-called voicing lockwhich must be operated before a sound test bar for a voiced sound may beactuated and also a stop consonant lock which must be operated before asound test bar representing a stop con-.

sonant may be actuated. The voicing lock comprises an electromagnet 6|connected to the output of filter 50 and as previously described theoutput current of filter 50 is substantially zero for unvoiced soundswhile its output is of substantial amplitude for all voiced sounds.Hence,

electromagnet 6| will be energized only for voiced sounds.

Connected across. the output of vogad 46 in parallel with channel 48 isanother channel 62 leading to an electromagnet 03 constituting a part ofthe stop consonant lock. Channel 62 includes an amplifier 64 to isolatechannel 82 fromthe other circuits connected across the output terminalsof vogad 48. The output of amplifier 64 is rectified by rectifier l5 andis then impressed on the low-pass filter 66 which passes the band from 0to 80 cycles per second 'to eliminate the fundamental frequency of anyvoiced sound;

and the conductors between filter 06 and the input of low frequencyamplifier 01 are shunted by a large inductance 68 with electromagnet itresponsive to the output of "amplifier 61. When a sudden change in. the.received energy level such as caused by a stop consonant sound is re- 40ceived by channel 02 a sudden pulse of energy goes through circuit 62and builds up a potential across inductance 68 which being amplified byamplifier II will cause electromagnet 03 to operate. However, thesustained power level] of a voiced sound will not produce sufficientpotential across inductance 60 to cause the operation of electromagnet83. The manner in which electromagnets ti and It function in preventingfalse operation will be described later.

Referring now to Fig. 4 it will be seen that the resonance bars C1 to Cmare mounted one above the otherin a suitable manner to enable eachresonance bar to move along a certain path when its. associatedelectromagnet S1 to $10 is energized each resonance bar being biased bya spring 54 to a normal position with the left end of slot 55 againststop pin 56 and with the maximum movement of any resonance bardetermined by the length of slot 55.

60 These resonance bars C1 to Clo and certain parts of the associatedapparatus are somewhat similar to teletypewrlter apparatus-as disclosed-in Lang et al. U. 8. Patent 2,106,805 of February 1, 1938, or Morgan eta1. U. S. Patent 1,745,633 of February 4, 1930, except that the codebars of a; teletypewrlter are fewer in number and occupy only twopossible positions, an operate position and a non-operate position,while each resonance bar C1 to Cm is designed to be advanced over a widerange of positions including not only its filters F1 to Fit dueto theincreasing width of The apparatus of Figs. 1, to 3 begins to tune.

- on Sound printing mechanisms. movement of main bail 18 causes allsound test ensues tion for analyzing and registering the spoken messageas soon as line finder 4 I has established connection with the callingline to complete an obvious energizing circuit for the high impedancerelay 59 connected across the conductors 48 leading to the voiceoperated register sender. The energization ofrelay 59 serves to connectground to conductor 1| thereby energizing clutch magnet is to bring intocontact the parts of clutch 12' f whereby motor 13 is capable ofrotating the drive shaft 14 at the desired speed. The consequentrotation of cam 15 forces lever 16 back and forth thereby causing themain bail plunger 11 to move up and down and cause the main bail 18 ofFig. 4 to execute a similar upward and downward movement. For a moredetailed description of the operation of main ball 18 in testing theresonance bars C1 to C10 reference may be had tomy U; S..Patent No.2,195,081 of March 26 1940, Each upward bars 80 to test the setting ofthe'resonance bars C1 to C10, there being a sound test bar 80 for eachphonetic sound to be registered although for simplication purposes onlytwo sound .test bars are completely shown in Fig. 4.

As shown in Fig. 4 each sound test bar 80 has a spring M which tends tomove the sound test bar downwardly and rearwardly and hold the soundtest bar in normal position as shown in Fig. 4 with the sound test barpressed against the forward edge of the main bail 18 when the main bailis in its normal position. It will also be noted from Fig. 4 that withthe sound test bars in normal position an intermediate portion 82 ofeach sound test bar lies in front of but spaced slightly from theslotted inner edges of the resonance bars C1 to C10.

Main bail 18 as previously described is continually being raised andlowered by plunger "I'I after the energization of clutch magnet It. As

ball 18 starts to move upwardly as in Fig. 7 this upward movement due tocam surface 83 on each sound test bar enables springs 8| to move allsound test bars 80 rearwardly against the notched front edges of theresonance bars C1 to C10 as shown in Fig. 7. It may be assumed thatelectromagnets S1 to S c have moved resonancebars C1 to C10 to suchpositions as to permit one of the sound test bars 80 tov drop into theslots (see Fig. 8) far enough to bring, its rearwardly projecting lugtsinto the path of. movement of the main ball 18. "Upon thecontinuedupward movement of main bail 18 its forward edge engages lug 8dof the selected sound test bar andlmoves the s lected sound test barupwardly (see Fig. 9) t reby causing the horizontal arm 85 of theselected sound test bar to enter slots in the lower edges of the sixhorizontally arranged coding bars SB1SB6 and cause the selectivelongitudinal movement of these six coding bars in a manner which will bedescribed later. The latter part of the upward movement-oi the selectedsound test bar to causes lug B4 to engage a stationary lug 81 whichthrows the selected sound test bar forwardly and outoi the notches inthe resonance bars as shown in Fig. 10 whereby the resonance bars may bereactuated for another alignment to provide for the later selection ofanother sound test bar. Spring 8| thereupon lowers the selected soundtest bar to'its normal positiom as shown in Fig. 11 in which the mainbail i8 is shown as returned to its starting position.

Inasmuch as it is contemplated that the freetition lockout whereby afterone sound test bai 80 has entered the slots in the resonance bars thesaid one sound test bar cannot reenter the V slots until there has beena realignment of at least one of the resonance bars. Associated witheach sound test bar 80 is an anti-repeat bar at pivoted on a stationarypin 80. The upper portion 9! of each anti-repeat bar 88 is biasedtowards the rear edges of the resonance bars due to a biasing spring 92.The rear edges of the resonance bars 01 to C10 are also provided withshallow slots as will be described later so that when the resonance barsoccupy positions to enable a. selected sound testbar 80 to enter slotsin the front edges of the resonance bars, all the resonance bars willhave aligned slots in their rear edges to permit the entrance of theantirepeat bar 88 associated with the particular sound bar so is in itsnormal position as in Fig. 6 the associated anti-repeat bar 88 isprevented from entering any slots in the resonance bars since thereispivoted to the lower end of each sound test bar at a spring latch asengaging a hook at on the lower end of the anti-repeat bar as.

As soon as any sound test'bar 80 after entering the aligned slots in thefront edges or the resonance bars has. been pulled upwardly due to themain ball is engaging lug 84 (Fig. 9) the latch 93 is lifted freeof'hook 9d, and spring as then causes the associated anti-repeat bar toenter the aligned slots in the rear edges of the resonance bars. Pivotedto the upper end of 40 each anti-repeat bar as is an angular lever 95biased by spring 95120 the position shownin Figf 6 with its arm .91extending towards but not contacting with the associated sound test bar80 as long as the sound test bar and the antirepeat bar are in theirnormal positions of Fig. 6. When the initial movement of the main ball88 has permitted a sound test bar to enter the aligned slots in theresonance bars this rearward movement of such a sound test bar allows50. arm 91 to ride on the upper surface of lug 98' as shown in Fig. 8.When, any sound test bar til is lifted upwardly (Figs. 9 and 10) lug 98passes above arm 91 and since the associated anti-repeat bar 8$ is nowallowed to enter the aligned slots in the rear edges of the resonancebars the subsequent lowering of the sound test bar 86 after theselective actuation of the cod'-. ing bars SE1 toS Ba as in Fig. 1 1causes arm 81 to be caught-by lugdd as long as the antirepeat bar 9-8lies in the slots in the resonance bars. Arm 9], therefore, prevents thesound test bar 80 from entering the. slots in the front edges ofqtheresonance bars a second time as long as its associated anti-repeat bar58 is lying in the aligned slots in the rear edges of the resonancebars. It' will also be notedfrom Fig. Lithat with the sound test bar 8%retracted after the selective setting of coding bars 831 r to $36 andwith the associated anti repeat bar 86 lying in the slots in theresonance bars, the

spring latch 93 rests upon the tip of hook 96.

However, as soon as any one of the resonance bars C1 to C10 is moved toa new position by the energization or deenergization of one of theelectromagnets -S1 to 510, such a movement of test bar. However, as longas each sound test"

